Pull arsenic from drinking water and convert to bricks

MORE than 100 million people around the world are exposed to dangerous levels of arsenic, which is found naturally in groundwater but has no obvious taste or odour. Its effects build up over time, slowly poisoning the body and leading to serious problems like heart disease, cancer and reproductive issues. Now a project aims to filter it out of drinking water – and lock it up in the concrete of new buildings.

A team at the University of California, Berkeley, is planning a trial to filter 10,000 litres of water every day in rural sites across India. Susan Amrose and her team have designed a container that can hold 600 litres of water pumped in directly from a nearby well. Inside, it is fitted with a series of steel plates. A small voltage runs through the plates, making them rust more quickly. Arsenic binds to the rust as it forms and falls to the bottom of tank, where it is collected as rusty sludge. The treated water is then pumped out.

The technology has already been tested at a rural high school in Dhopdhopi, south of Kolkata, and now the team plans to start a year-long trial in which local people manage the filtration themselves. To get rid of the hazardous sludge, the group is partnering with local concrete companies. The waste does not make the concrete dangerous, although they are testing to see if the material's strength is affected.

"I think stabilising hazardous waste in concrete is something that's going to become more common. It makes sense, because there are so many roads being built in India right now," says Amrose.

Rick Johnston of the World Health Organization says that for many people in developing Asian countries such as Bangladesh, India and Nepal, water filtration is not always a top priority. "It's hard to balance a long-term risk with short-term issues that are immediately visible like food, electricity and education," he says. "It's too easy to put a risk like arsenic on the back-burner."

But the system is not just for poorer nations. The team is considering creating a prototype for filtering drinking water in parts of California, such as the San Joaquin Valley, where arsenic levels are high.

This article appeared in print under the headline "Stealth toxin coaxed from drinking water"

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